The invention will be described in the context of a car door, but it could also be used with other closures such as trunks/tailgates, or with other types of vehicles such as boats or aircraft. In a broad sense, the invention may also be used in non-vehicle applications.
A relatively recent development in the design of vehicle door handles is the retractable handle in which a flush-mounted handle is retractably mounted to the vehicle door such that the handle is flush with an outer door skin of the vehicle. This means that the handle can move between two states: a stowed or retracted state in which the handle is flush-mounted and a deployed or extended state in which the handle protrudes from the surrounding door surface so that it may be grasped by a user.
Once the handle is in the deployed state, it can be pulled, usually against a spring bias, to move the handle towards a third, operative, state to unlatch the door. In moving to the operative state the handle may unlatch the door mechanically, for example by acting on a Bowden cable coupled to the door latch, or electrically by acting on an electrical switch coupled to the latch. Examples of such a vehicle door handle are described in the applicant's co-pending US patent application no. US2013/0241215 A1 and published PCT application no. WO2012/175647.
In the context of retractable door handles, the handles themselves may be movable between the stowed and deployed states mechanically or by electrical means. For example, in a handle arrangement used in some cars, a flush-mounted handle comprises a bar-like handle pivotally attached near one of its ends to a door. In the stowed state the handle lies flush with the door skin and, in the deployed state, the major portion of the handle pivots away from the door skin so that a user can grasp the handle and pull it further into the operative state to unlatch the door. A user moves the handle between the stowed and deployed states simply by pressing the front end of the handle against a spring bias so that the rear portion pivots outwardly. Although this scheme provides a relatively simple mechanical action, it is rather unintuitive to use and requires a two-handed operation which is undesirable.
In contrast, an electrically-actuated scheme is implemented in some other cars. Here, a flush-mounted strap-type handle is actuated electrically between a stowed state in which the outer surface of the handle is flush with the door skin and a deployed state in which the outer surface of the handle is spaced from the door skin and so reveals a grab-loop which can be grasped by a user. The handle is moved from the stowed to the deployed state by means of a sensing system which senses the presence of a person next to the door or about to grab the handle. The sensing system may also be configured to command the handle into a deployed state in response to a deployment signal transmitted by a suitable control device, e.g. a remote key fob of the vehicle.
Since the handle is activated automatically and deploys into a deployed state without mechanical input from a user, it is intuitive to use and offers a characteristic ‘surprise and delight’ feature of the vehicle. However, when a handle is powered electrically, there is a potential problem when electrical power is unavailable.
It is against this background that the invention has been devised.